Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$89.37	8.363%	$96.844	$96.84	$96.85	$96.80
Purchase #2	$191.94	5.583%	$202.656	$202.66	$202.65	$202.70
Purchase #3	$235.95	10.209%	$260.0381	$260.04	$260.05	$260.00
Purchase #4	$181.60	5.521%	$191.6261	$191.63	$191.65	$191.60
Purchase #5	$104.78	7.431%	$112.5662	$112.57	$112.55	$112.60
Purchase #6	$38.42	13.250%	$43.5107	$43.51	$43.50	$43.50
Purchase #7	$171.50	4.474%	$179.1729	$179.17	$179.15	$179.20
7 purchase totals =	$1,013.56		$1,086.4140	$1,086.42	$1,086.40	$1,086.40